1. The Field of the Invention
The present invention relates to computer communications networks. More specifically, the present invention relates to methods of prioritizing data transmissions.
2. The Relevant Technology
Computer technology is breaking barriers to inter-personal communications at an amazing rate. Already, it is possible to communicate almost instantaneously with anyone in the world that has a computer and a telephone line. Computer networks, such as the Internet, link individuals and various types of organizations in world-wide digital communication The Internet has almost unlimited promise for communications advances, but is limited by an overburdened and somewhat unsuited transmission medium.
In addition to the Internet, businesses, educational institutions, government agencies, and other similarly related entities also communicate over much smaller-scale networks, such as local area networks (LANs) and wide area networks (WANs). These small-scale networks, particularly LANS, operate at much higher speeds than the Internet, but are expensive to operate at large scales. Thus, a large gap exists, between the scope of coverage and speed of operation of the global, but relatively slow, Internet and the faster but more limited LANs and WANs. It would be advantageous to close this gap with larger-scale networks that operate at speeds close to that of LANS.
Several barriers exist to filling the gap between current limited coverage networks and the Internet. One such barrier is the “last mile” dilemma. That is, the Internet runs at very high speeds over its backbone, but slows down considerably over its localized connections. Generally, the Internet relies upon standard telecommunications industry lines and switching equipment for this last mile. This infrastructure is designed for telephone communications, and is not well adapted to the packetized communications of digital networks. A dilemma lies, however, in replacing, the telephone infrastructure with transmission mediums more suited to digital communications. It is currently considered prohibitively expensive to connect high speed communications lines down to the individual users of the Internet.
This fact, together with the general congestion of the Internet in general leads to a substantial slow down of Internet communications. It also limits the deployment of intermediate types of networks. A further barrier to the implementation of networks of varying scopes and to the new introduction of new paradigms for network communication comes in the form of financing. Such developments using current technology would be prohibitively expensive. Who is going to pay for this infrastructure?
Accordingly, a need exists for an intermediate sized network to close the gap between the world-wide Internet and current relatively small scale networks. Preferably, such an intermediate sized network operates at speeds similar to those of LANS, coverage both in geographical area and diversify of user type. Additionally any solution to this problem should also address financing of installation and should overcome the last mile dilemma. New technologies for achieving such a new paradigm in computer networking are similarly needed.
In addition to the lack of larger scale, high-speed networking, prior art networks of every size have additional problems. Many of these problems result from the way in which switching is carried out by known networks. Switches are simply junctions for multiple communication lines. A “data transmission” is simply an analog or digital signal sent from an origin to a destination. Bundled data transmissions, or “packets,” arrive at an incoming port of the switch, and are routed to the proper outgoing port to reach their destination. (Although each port is capable of two-way communication, the port through which a packet arrives is designated as the incoming port, while that port through which it will exit is the outgoing port.) A data transmission from one computer to another may pass through several switches, depending on the size of the network involved. Full-duplex, switched networks are generally far faster than their half-duplex, unswitched counterparts.
However, a special problem arises when multiple packets simultaneously arrive at a switch through different incoming ports, and all of the packets must go through the same outgoing port. Since a line is only capable of conveying a single packet at a time, one packet will be sent while the rest wait. Current networking systems possess significant drawbacks in that they entirely fail to prioritize, or prioritize improperly, the order in which the packets are transmitted.
This has many undesirable effects. Since the switches are typically utilized in a branching network, many more switches may be downstream from the outgoing port. The switch itself is unaware of what type of destination any packet is sent to. The destination may be a server hosting many users simultaneously, or it may be a single home user.
As a result, people waiting for critical communications are forced to wait for other, less important traffic. For example, a company may have a large number of employees receiving e-mail through a server on the network. The e-mails may contain important instructions, information, questions, etc. that should not be delayed. However, if the e-mail is routed through the same switch as a large file download requested by a computer near the mail server, i.e., at the same outgoing port, the e-mail traffic may be slowed down by waiting for the file download. This occurs even though delays are inconsequential for the download, which will require several minutes in any case. Similarly, a number of computer users performing research over the Internet, using a variety of different sites, may be slowed down by a single user transmitting real time game data to another user.
No previously known system provides a sufficient solution to this problem. Simply sending packets through the port in sequential, cyclical form, or “round robin” form, provides equal time to each communication through the switch, and causes the problems described above. Giving priority to the heaviest user, i.e., the destination that has received the most packets, is inadequate because the volume of data is not proportional to its importance.
Thus, a there is a need, unfulfilled by the prior art, for a new method for prioritizing transmission of packets from a switching station. The method should preferably prioritize transmission according to the destination that is receiving the most important, i.e. time critical, information, while avoiding entirely blocking other destinations for lengthy periods of time. In addition, hardware and suitable data structures are needed for carrying out the method described above.
Another problem with known networks is broadcasting. Broadcasting occurs when a packet is sent to an unresolved destination. Communications over the Internet often take place on the third, or network layer of the ISO/OSI model, which is the Internetwork, or IP layer, of the TCP model. Transmissions may be addressed to a certain IP address, but the IP address is a property of the network, and may not be the same for a given device every time. Internet service providers (ISP's), for example, will often assign a temporary IP address to each individual dialed up computer.
In order to successfully route a packet to the proper device, a switch must have access to the hardware, or MAC address of the device, which is unique to each individual network interface card (NIC) that connects a computer to the network. The MAC address corresponds with the second layer of the ISO/OSI and TCP models. A computer sending a transmission may not always have access to the receiver's hardware address.
Thus, the sending computer sends an address resolution protocol (ARP) broadcast, or packet without a specific MAC address destination, which will then be propagated to multiple computers. The ARP broadcast contains a designated IP address for the destination computer, and acts as a request for a requested MAC address of the computer that has that IP address. The computer that has the IP address responds by sending a packet back to the origin of the broadcast, with its MAC address included in the packet. The computers can then communicate directly over the network without broadcasting to other users.
The problem with ARP broadcasting is that it creates a great deal of unnecessary traffic on a system. The ARP broadcast itself typically does not contain a great deal of data, but it must be transmitted to many computers, thereby occupying a great deal of bandwidth. Even if a receiving computer's MAC address is resolved by one transmitting computer on the network, another transmitting computer may transmit data to the computer, thus requiring another ARP broadcast. In a network or branch with a large number of users, a great deal of the network's bandwidth may be occupied by ARP broadcasting.
Consequently, it would be an advancement in the art to provide a method and apparatus capable of reducing ARP broadcasting. The method and apparatus should enable transmitting computers to obtain the MAC addresses of computers to which they will send data, without propagating every ARP broadcast to every computer. Furthermore, the method and apparatus should preferably reduce ARP broadcasting without the need to replace a great deal of the currently-existing network infrastructure. The method and apparatus should be inexpensive, low-maintenance, and fast. Finally, the method should be fully compliant with existing protocols for network data transmission, so as to be transparent to computers and end users on the network.